Resilient, compressible gaskets are typically utilized in cored manholes to provide a water-tight seal between a manhole opening and a pipe extending therethrough.
Manholes are often cored in situ by coring equipment used in the field. Openings in the sidewalls of manholes which are cored in the field typically have wider tolerance ranges than those which are cast in the factory, necessitating the use of gaskets which are capable of providing a good water-tight seal in situations where the gap space between an inner diameter of a cored opening and an outer diameter of a pipe falls within a broader tolerance range.
The prior gaskets utilized in cored manholes typically have a hollow annular cavity whose volume decreases as it changes in cross section due to radial compression when force-fitted between the cored opening in the manhole sidewall and the pipe. In such applications it was necessary to provide a pipe whose outer diameter was more precise relative to the inner diameter of the cored opening, making it difficult to provide an adequate water-tight seal in cored openings wherein the aforesaid gap space falls in a wider tolerance range.